The present invention relates to the improvement of a hard disk testing apparatus and method.
In the conventional quality test of magnetic disks such as hard disk (hereinafter called as "disks"), while a head is shifted by a carriage reciprocatively provided in the direction of the radius of a disk, test signals (information) are magnetically written in the surface of the disk, the written signals are read by a magnetic head, and based on the result of reading, several test items such as missing pulse errors, extra pulse errors, etc. are tested.
In order to reduce the testing time in this case, the heads (for example two heads) are fixed to a head mounting board with fixing jigs at intervals obtained by equally dividing the radius of the disk.
The head mounting board is provided at one end of a carriage which is constructed in the manner that it can be reciprocated in the direction of the center of the disk.
Therefore, the whole test for a disk is completed by shifting the head by, for example, a half of the radius of the disk in case there are two heads.
The above-mentioned test is carried out for several thousands tracks (magnetic concentric circles) provided in the disk and the test results are totalized in order to control the quality of disks.
In the conventional disk testing apparatus, several heads are fixed to a head mounting board with fixing jigs at predetermined equal intervals. However because of fixing errors, the heads may not be set at the predetermined intervals. As a result, even if the head is shifted by the predetermined distance, it happens that tracks around the border between the test ranges covered by one head and the other may be doubly tested or may not be tested.
There is another adjusting method in which the separation between the heads fixed to the head fixing board is first measured, and based on the measured separation, the positions of the heads are adjusted by a micro adjusting mechanism. However, even by this method, the same problems may occur because of errors in the micro adjustment mechanism.